1. Technical Field
The present invention relates generally to an apparatus and method for estimating the direction of an RF signal and, more particularly, to an apparatus and method for estimating the direction of an RF signal via a slit antenna or multiple-input and multiple-output (MIMO) antennas.
2. Description of the Related Art
Methods of estimating the direction of a signal include a method using a directional antenna and a method using a MIMO antenna array.
The method using a directional antenna is a technique for estimating the direction of a signal using a gyro or a compass based on the characteristic in which a directional antenna itself exhibits a gain direction in a specific direction. Directional antennas include a dish type, such as a satellite antenna, an array type, such as a Yagi antenna, and a curved type antenna for the concentration of signals. The method using the directional antenna can estimate the direction of a signal using a technique for enhancing the gain of the antenna in a specific direction.
In contrast, a technique for independently receiving signals of MIMO antennas, combining the received signals, assigning weights so that the magnitude of a specific signal is maximized, and merging the signals of the antennas is referred to as a beamforming technique.
The beamforming technique is widely used recently because it is advantageous in that the pattern of signal reception gain may be controlled by controlling a weight applied to each antenna even without directly rotating the direction of an antenna.
When signals of antennas are independently received, as in a beamforming technique, an MIMO antenna type technique is implemented using spatial multiplexing as in recent mobile communication, and a larger amount of data can be transmitted and received using the MIMO antenna type technique. As another technique, a method of combining independent signals based on fixed weights is also used to obtain diversity gain regarding signals.
For example, Korean Patent Application Publication No. 2012-0035907 entitled “Apparatus for Software-Defined Radio Terminal Supporting Direction of Arrival Estimation Algorithms and Method for Distributing and Installing Software-Defined Radio Terminal Applications” describes a software-defined radio (SDR) terminal of an SDR MIMO antenna system for the direction of arrival (DOA) and a method of distributing and installing SDR terminal applications.
If MIMO antennas are used, a number of RF receivers equal to the number of MIMO antennas are used. Accordingly, a disadvantage arises in that the complexity of hardware increases by the number of MIMO antennas. One technique that has been proposed to deal with this disadvantage is to split each antenna in terms of time and then collect signals. That is, signals received from respective antennas are not sampled at the same time, but the signals are sequentially received from the respective antennas on a per-sample basis. In this case, processing can be performed by increasing a sampling rate according to the number of antennas, instead of increasing the complexity of hardware.